U.S. patent number 7,521,718 [Application Number 11/654,636] was granted by the patent office on 2009-04-21 for organic light emitting display.
This patent grant is currently assigned to LG Electronics Inc.. Invention is credited to Sun Kil Kang, Changnam Kim, Honggyu Kim, Sangkyoon Kim.
United States Patent |
7,521,718 |
Kang , et al. |
April 21, 2009 |
Organic light emitting display
Abstract
Provided is an organic light emitting display, comprising a
substrate; a driving unit formed over the substrate; a
planarization layer formed over the driving unit, the planarization
layer comprising a normal tapered edge portion; and an emission
unit formed over the planarization layer to be electrically
connected to the driving unit.
Inventors: |
Kang; Sun Kil (Anyang-si,
KR), Kim; Changnam (Seoul, KR), Kim;
Honggyu (Urwang-si, KR), Kim; Sangkyoon
(Hanam-si, KR) |
Assignee: |
LG Electronics Inc. (Seoul,
KR)
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Family
ID: |
38262346 |
Appl.
No.: |
11/654,636 |
Filed: |
January 18, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070164294 A1 |
Jul 19, 2007 |
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Foreign Application Priority Data
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Jan 19, 2006 [KR] |
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10-2006-0006007 |
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Current U.S.
Class: |
257/79; 438/153;
438/149; 257/72 |
Current CPC
Class: |
H01L
51/524 (20130101) |
Current International
Class: |
H01L
27/15 (20060101) |
Field of
Search: |
;257/79,59,72
;438/149,153,257 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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10-2006-0000363 |
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Jan 2006 |
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KR |
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Primary Examiner: Smith; Matthew
Assistant Examiner: Rodgers; Colleen E
Attorney, Agent or Firm: KED & Associates LLP
Claims
What is claimed is:
1. An organic light emitting display comprising: a substrate; a
driving unit formed over the substrate; a planarization layer
formed over the driving unit, the planarization layer comprising a
normal tapered edge portion; an emission unit formed over the
planarization layer to be electrically connected to the driving
unit; and a passivation layer formed over the planarization layer
to cover the emission unit and the planarization layer, wherein the
tapered edge portion of the planarization layer is in contact with
the passivation layer.
2. The organic light emitting display of claim 1, wherein a taper
angle of the edge portion of the planarization layer is about 15
degrees to 60 degrees.
3. The organic light emitting display of claim 1, wherein a taper
angle of the edge portion of the planarization layer is about 15
degrees to 30 degrees.
4. The organic light emitting display of claim 1, wherein the
planarization layer comprises one selected from a group consisting
of a poly acryl-based resin, a polyimide-based resin, a
benzocyclobutene-based resin, and a spin on glass (SOG).
5. The organic light emitting display of claim 1, wherein the
passivation layer comprises a normal tapered edge portion, wherein
a taper angle of the edge portion of the passivation layer is about
15 degrees to 60 degrees.
6. The organic light emitting display of claim 5, wherein the taper
angle of the edge portion of the passivation layer is about 15
degrees to 30 degrees.
7. The organic light emitting display of claim 5, wherein a taper
angle of the edge portion of the passivation layer is substantially
the same as a taper angle of the edge portion of the planarization
layer.
8. The organic light emitting display of claim 5, wherein a taper
angle of the edge portion of the passivation layer is less than a
taper angle of the edge portion of the planarization layer.
9. The organic light emitting display of claim 1, wherein the
driving unit comprises at least a thin film transistor, wherein the
thin film transistor comprises an active layer comprising amorphous
silicon.
10. The organic light emitting display of claim 1, wherein the
emission unit comprises a first electrode, an organic emitting
layer and a second electrode.
11. The organic light emitting display of claim 10, wherein the
first electrode is an anode comprising a metal layer and a
transparent conductive oxide layer having a high work function.
12. The organic light emitting display of claim 11, wherein the
transparent oxide layer comprises one selected from a group
consisting of ITO, IZO, ICO and ZnO.
13. The organic light emitting display of claim 11, wherein the
second electrode is a cathode and a transflective electrode
comprising a metal having a low work function.
14. The organic light emitting display of claim 13, wherein the
metal comprises one selected from a group consisting of Mg, Ag, Al,
Ca and an alloy thereof.
15. The organic light emitting display of claim 10, wherein the
first electrode is a cathode comprising a metal having a low work
function.
16. The organic light emitting display of claim 15, wherein the
second electrode is an anode comprising a transparent conductive
oxide layer having a high work function.
17. The organic light emitting display of claim 1, further
comprising a cover substrate attached to the substrate with a
sealant.
18. The organic light emitting display of claim 17, wherein the
cover substrate is a transparent substrate comprising glass or
plastic.
19. The organic light emitting display of claim 17, wherein the
sealant comprises a normal tapered edge portion.
20. The organic light emitting display of claim 1, wherein the
tapered edge portion of the planarization layer contacts an area
separated from the emission unit.
21. The organic light emitting display of claim 20, wherein the
tapered edge portion of the planarization layer is located at a
terminal end of the planarization layer that is not in contact with
the emission unit.
22. The organic light emitting display of claim 1, wherein the
tapered edge portion of the planarization layer slants away from
the driving unit.
23. The organic light emitting display of claim 1, wherein the
passivation layer has a tapered edge portion that contacts the
tapered edge portion of the planarization layer.
24. The organic light emitting display of claim 23, wherein the
edge portions of the passivation layer and the planarization layer
taper at substantially the same angle.
25. The organic light emitting display of claim 23, wherein the
edge portions of the passivation layer and the planarization layer
taper at different angles.
26. The organic light emitting display of claim 1, further
comprising: a sealant formed over the passivation and planarization
layers, wherein the sealant has an edge portion that tapers at a
different angle than the tapered edge portions of the passivation
and planarization layers.
27. The organic light emitting display of claim 1, wherein the
tapered edge portion of the planarization layer is located between
terminal ends of a cover substrate and a base substrate, the
emission unit located between the cover and base substrates.
28. The organic light emitting display of claim 1, wherein the
tapered edge portion of the planarization layer is located between
an end of an electrode of the emission unit and a barrier rib.
29. An organic light emitting display comprising: a substrate; a
driving unit on the substrate; a planarization layer, on the
driving unit, having a tapered edge portion; an emission unit on
the planarization layer to electrically couple with the driving
unit; and a passivation layer on the planarization layer to cover
the emission unit and the planarization layer, wherein the tapered
edge portion of the planarization layer contacts the passivation
layer.
30. The organic light emitting display of claim 29, wherein a taper
angle of the edge portion of the planarization layer is
approximately 15 degrees to 60 degrees.
Description
This nonprovisional application claims priority under 35 U.S.C.
.sctn. 119(a) on Patent Application No. 10-2006-0006007 filed in
Republic of Korea on Jan. 19, 2006 the entire contents of which are
hereby incorporated by reference.
BACKGROUND
1. Field
The present invention relates to an organic light emitting display
(OLED).
2. Related Art
In general, an organic light emitting display is a self-emitting
display for emitting light by electrically exciting a fluorescent
compound and has been spotlighted as a future generation display
that can solve problems of a liquid crystal display as it can be
driven in a low voltage, easily reduce a thickness, have a wide
viewing angle and a fast response speed, etc.
The organic light emitting display comprises an organic emitting
layer between an anode and a cathode. The organic light emitting
display forms an exciton, which is a hole-electron pair, by
coupling a hole received from the anode and an electron received
from the cathode within the organic light emitting layer and emits
light by generating energy when the exciton returns to a ground
level. The organic light emitting display further comprises a hole
(electron) injecting layer and/or a hole (electron) transporting
layer between the anode or the cathode and the emitting layer.
Depending on a driving mode, an OLED is usually classified into a
passive matrix organic light emitting display (PMOLED) and an
active matrix organic light emitting display (AMOLED).
FIG. 1 illustrates a conventional OLED 100.
Referring FIG. 1, a driving unit 130 is formed over a substrate 100
and a planarization layer 150 is formed on the driving unit.
The driving unit 130 comprises at least a thin film transistor for
driving. The thin film transistor comprises a gate electrode 131, a
gate insulation layer 132, an active layer 133 made of amorphous
silicon, an ohmic contact layer 134, a source electrode 135 and a
drain electrode 136.
An emission unit 140 is formed on the planarization layer 150 to be
connected to the driving unit 130. The emission unit 140 comprises
a first electrode 141 connected to the drain electrode 136, an
organic emitting layer 143 and a second electrode 144.
An insulating layer 142 is formed on the first electrode 141
exposing a portion of the first electrode 141. The organic emitting
layer 143 is formed on the exposed portion of the first electrode
141.
A passivation layer 160 is formed on the emission unit 140 to cover
the emission unit 140 and the planarization layer 150. A cover
substrate 120 is attached to the substrate 110 comprising the
passivation layer 160. The substrate 110 and the cover substrate
120 are attached with a sealant 170.
Moisture and oxygen penetrating inside the OLED may damage the
organic emitting layer and the electrodes. More specifically,
moisture passes into a pin hole formed in a portion of a cathode or
into an edge portion between the cathode and a barrier rib, and
reacts with organic layer and the electrodes, thereby generating
hydrogen.
Such hydrogen diffuses to the left and right sides on an interface
between the cathode and the organic emitting layer, causing
generation of bubbles over the organic emitting layer. As a result,
an event in which the cathode is lifted up occurs frequently. Also,
when oxygen transmits through the pin hole of the cathode or the
edge portions between the cathode and a barrier rib, an oxide layer
is likely to be formed on the cathode at the interface between the
cathode and the organic emitting layer. This oxide layer often
shields a flow of current.
In the above described conventional OLED 100, the passivation layer
160 is formed to protect the driving unit 130 and the emission unit
140. Particularly, an edge portion of the passivation layer 160 is
formed to be inclined inwardly. In other words, the passivation
layer comprises a normal tapered edge portion. However, since an
edge portion of the planarization layer 150 are formed to have
corners nearly perpendicular, the passivation layer 160 is not well
deposited on the edge portions of the planarization layer 150. As a
result, adhesion between the planarization layer 150 and the
passivation layer generally becomes poor.
Accordingly, the driving unit 130 and the emission unit 140 may not
be effectively protected by the passivation layer 160, because
moisture and oxygen are more likely to penetrate into the devices
from the outside through the passivation layer 160
SUMMARY
Accordingly, the present invention is provided an organic light
emitting display, comprising a substrate; a driving unit formed
over the substrate; a planarization layer formed over the driving
unit, the planarization layer comprising a normal tapered edge
portion; and an emission unit formed over the planarization layer
to be electrically connected to the driving unit.
A taper angle of the edge portion of the planarization layer may be
15 degrees to 60 degrees.
The planarization layer may comprise one selected from a group
consisting of a poly acryl-based resin, a polyimide-based resin,
and a benzocyclobutene-based resin.
The organic light emitting display further comprises a passivation
layer covering the emission unit and the planarization layer.
The passivation layer comprises a normal tapered edge portion.
A taper angle of the edge portion of the passivation layer is
substantially the same as a taper angle of the edge portion of the
planarization layer.
The organic light emitting display further comprises a cover
substrate attached to the substrate with a sealant.
The sealant comprises a normal tapered edge portion.
Detailed features and advantages of the present invention will be
fully described in the foregoing embodiments of the present
invention and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are comprised to provide a further
understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention. In the drawings:
FIG. 1 illustrates a conventional organic light emitting display
(OLED);
FIG. 2 illustrates an organic light emitting display (OLED)
according to an embodiment of the present invention; and
FIG. 3 illustrates an organic light emitting display (OLED)
according to another embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS
Various embodiments of an organic light emitting display (OLED)
according to the present invention will be described in a more
detailed manner with reference to the attached drawings.
FIG. 2 illustrates an OLED 200 according to an embodiment of the
present invention.
Referring to FIG. 2, a driving unit 230 and an emission unit 240
are formed over a substrate 210.
The driving unit 230 comprises at least a thin film transistor for
driving. The thin film transistor comprises a gate electrode 231
formed over a substrate 210, a gate insulation layer 132 formed
over a substrate 210 comprising a gate electrode 231. An active
layer 233 made of amorphous silicon is formed over the gate
insulation layer 132 to correspond to the gate electrode 231. An
ohmic contact layer 234 is formed over on both sides of the active
layer 233 the gate 231. A source 235 and a drain 236 are formed
over respective portions of the ohmic contact layer 234.
Although not shown, the driving unit 230 further comprises a thin
film transistor for switching and a capacitor.
A planarization layer 250 is formed over the substrate 210
comprising the driving unit 230 to obviate the height difference of
the substrate 210 comprising the driving unit 230.
The planarization layer 250 may include an organic material. For
instance, the planarization layer 250 includes one selected from a
group consisting of a polyacryl-based resin, a polyimide-based
resin, and a benzocyclobutene (BCB)-based resin.
On the other hand, the planarization layer 250 may include an
inorganic material. For instance, the planarization layer 250
includes SOG (spin on glass).
The planarization layer 250 may comprise a normal tapered edge
portion. A taper angle r1 of the edge portion of the planarization
layer 250 may be about 15 degrees to 60 degrees. Preferably, a
taper angle r1 of the edge portion of the planarization layer 250
may be about 15 degrees to 30 degrees.
When the planarization layer 250 comprises a photosensitive
material, the edge portion of the planarization layer 250 is formed
to be inclined inwardly by exposure. When the planarization layer
250 comprises a non-photosensitive material, the edge portion of
the planarization layer 250 is formed to be inclined inwardly by
dry etching.
A contact hole 245 is formed in the planarization layer 250 to
expose a portion of the drain electrode 236, an emission unit 240
is formed over the planarization layer 250.
The emission unit 240 comprises a first electrode 241 connected to
the drain electrode 236 through the contact hole 245, an organic
emitting layer 243 and a second electrode 244.
When an OLED according to an embodiment of the present invention is
top-emission type, the first electrode 241 may be an anode
comprising a metal layer and a transparent conductive oxide layer
having a high work function. The transparent conductive oxide layer
comprises one selected from a group consisting of ITO, IZO, ICO and
ZnO. The second electrode 244 may be a cathode and transflective
electrode comprising a metal having a low work function. The metal
comprises one selected from a group consisting of Mg, Ag, Al, Ca
and alloy thereof.
On the other hand, the first electrode 241 may be a cathode
comprising a metal having a low work function, and the second
electrode 244 may be an anode comprising a transparent conductive
oxide layer having a high work function.
An insulating layer 242 is formed on the first electrode 241 to
expose a portion of the first electrode 241. The organic emitting
layer 243 is formed on the exposed portion of the first electrode
241.
Although not shown, a hole injection layer (HIL) and/or a hole
transport layer (HTL) may be formed between the first electrode 241
and the organic emitting layer 243, an electron transport layer
(ETL) and/or an electron injection layer (EIL) may be formed on the
organic emitting layer 243.
A passivation layer 260 is formed over the substrate 210 to cover
the emission unit 240 and the planarization layer 250. The
passivation layer 260 may comprise silicon nitride, silicon oxide
or multiple layers comprising silicon nitride and/or silicon oxide.
The passivation layer 260 is formed by sputtering or CVD (chemical
vapor deposition).
The passivation layer 260 comprises a normal tapered edge portion.
A taper angle r2 of the edge portion of the passivation layer 260
may be about 15 degrees to 60 degrees. Preferably, a taper angle r2
of the edge portion of the passivation layer 260 may be about 15
degrees to 30 degrees.
A taper angle r2 of the edge portion of the passivation layer 260
is substantially the same as a taper angle r1 of the edge portion
of the planarization layer 250. When the taper angles r1 is
substantially the same as the taper angle r2, step coverage
characteristic of the passivation layer 260 and adhesion between
the passivation layer 260 and the planarization layer 250 may
improve so that the passivation layer 260 formed on the edge
portion of the planarization layer 250 has a high degree of
thickness uniformity.
On the other hand, a taper angle r2 of the edge portion of the
passivation layer 260 is not the same as a taper angle r1 of the
edge portion of the planarization layer 250. For example, a taper
angle r2 of the edge portion of the passivation layer 260 is less
than a taper angle r1 of the edge portion of the planarization
layer 250. In this case, the thickness of the passivation layer
formed on the edge portion of the planarization layer 250 is
gradually increased toward the substrate 210, it may effectively
block penetration of moisture or oxygen by covering the contact
area of the planarization layer 250 and the substrate.
A cover substrate 220 is attached to the substrate 210 comprising
the passivation layer 260 with a sealant 270. The cover substrate
220 may be a transparent substrate comprising glass or plastic.
As described above, the organic light emitting display according to
an embodiment of the present invention comprises the planarization
layer 250 having a normal tapered edge portion. And because a taper
angle of the passivation layer 260 is substantially the same as
that of the planarization layer, a contact area between the
planarization layer 250 and the passivation layer 260 increases.
This increase in contact area improves adhesion between the
planarization layer 250 and the passivation layer 260, and thus,
those undesired effects, often caused by the penetration of
moisture or oxygen inside the devices, can be minimized.
FIG. 3 illustrates an OLED according to another embodiment of the
present invention.
Referring to FIG. 3, an OLED according to another embodiment of the
present invention comprises a driving unit 330, a planarization
layer 350 formed on the driving unit 330 and am emitting unit 340
formed on the planarization layer 350 to be connected to the
driving unit 330. The planarization layer 350 may comprises a
normal tapered edge portion.
The driving unit 330 comprises at least a thin film transistor for
driving, the thin film transistor comprises a gate electrode 331, a
gate insulation layer 332, an active layer 333 made of amorphous
silicon, an ohmic contact layer 334, a source electrode 335 and a
drain electrode 336. The emission unit 340 comprises a first
electrode 341 connected to the drain electrode 336, an organic
emitting layer 343 and a second electrode 344.
A passivation layer 360 is formed over the substrate 310 to cover
the emission unit 340 and the planarization layer 350. Also, the
passivation layer 360 comprises a normal tapered edge portion, a
taper angle r2 of the edge portion of the passivation layer 360 is
substantially the same as a taper angle r1 of the edge portion of
the planarization layer 350.
A cover substrate 320 is attached to the substrate 310 comprising
the passivation layer 360 with a sealant 370. When an OLED
according to another embodiment of the present invention is
top-emission type, the sealant 370 may be a face sealant which is
located on a space between the cover substrate 320 and the
substrate 310 comprising the passivation layer 360. Or, the sealant
370 may be an edge sealant which is located on an edge area between
the cover substrate 320 and the substrate 310.
The sealant 370 may comprise a normal tapered edge portion, it may
improve adhesion between the sealant 370 and the passivation layer
360.
Although it is illustrated in FIG. 3 that a taper angle r3 of the
edge portions portion of the sealant 370 does not coincide with the
taper angle r1 of the planarization layer 350 and the taper angle
r2 of the passivation layer 360, the edge portion of the sealant
370 may be inclined to a certain degree of angle.
According to embodiments of the present invention, the edge portion
of the planarization layer is formed to be inclined inwardly, the
edge portion of the passivation layer is formed to be inclined to
an angle substantially the same as the inclination angle of the
planarization layer. Thus, adhesion between the edge portions of
the planarization layer and the passivation layer can be improved,
and thus, penetration of moisture or oxygen can be blocked.
The invention being thus described, it will be obvious that the
same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
* * * * *